The present invention relates to a variable differential pressure control apparatus for a hydraulic system for selectively setting the hydraulic fluid pressure supplied to an accumulator or similar device, and for selectively setting the pressure differential between the upper and lower limits of pressure in the accumulator or similar device.
It is conventional practice to employ an unloading valve in the hydraulic circuit between an hydraulic pump and an accumulator for unloading the circuit when a selected maximum pressure has been reached in the accumulator. Likewise, it is known to employ control means so that the accumulator will automatically be recharged to its maximum pressure when the pressure in the accumulator has reached a preselected lower limit. However, the prior art has failed to provide suitable apparatus which will enable an operator of the hydraulic system to vary selectively the differential pressure to the accumulator in a simple and effective manner.